Patients seek treatment for dentofacial deformity with the expectation that their oral function, esthetics, and oral health will be improved and that their quality of life will be enhanced as a result of treatment. Findings from this project have led to significant progress in the treatment of dentofacial disharmony by quantitatively documenting the stability and clinical acceptability of various orthognathic surgery procedures and fixation methods used to treat dentofacial disharmonies. However, even with these advances, 1) clinically significant unacceptable post-surgery and post-treatment morphological changes occur in 5 to 20 percent of patients. The localization of the condylar and regional skeletal adaptations that occur after surgery and the effect of these adaptations and presenting clinical characteristics, procedural and/or demographic factors on the skeletal results at the end of treatment and after treatment is complete have not yet been characterized;2) virtually 100% of patients who have a mandibular osteotomy experience a neurosensory alteration in the short-term after surgery and, on average, quantitative measures of neurosensory assessment will not have returned to baseline values by two years. Although "surgical trauma" is generally cited as the cause, mandibular morphology and/or fixation screw placement may also be significant contributing factors;and 3) patients still experience a lengthy and uncomfortable recovery period following orthognathic surgery and the cost puts treatment out of reach for many patients. During this project period we will continue our use of the systematic, protocol-based, prospective observational study design using longitudinal quantitative three dimensional analyses of ConeBeamCTs. Specific Aim 1 is intended to assess the potential predictors (demographic, presenting clinical characteristics, type of surgery, pre and post-surgery condylar morphology and position, and regional areas of skeletal modeling) that underlie the clinically observed variation in positional skeletal adaptation over time. Specific Aim 2 is intended to assess the effect of mandibular morphology and fixation screw placement on post-surgical sensory alteration. Specific Aim 3 is intended to assess an emerging treatment intervention, Temporary Skeletal Anchorage, that is less costly and requires less recovery time than single jaw osteotomy as an alternative approach to treatment for specific dentofacial disharmonies. The clinical data from these three specific aims will advance our ultimate goal of improving the quality of treatment for patients with dentofacial deformities by improving clinical decision making and treatment planning for orthognathic surgery and by enhancing the ability of patients to make informed treatment choices. PUBLIC HEALTH RELEVANCE: The results from this proposal will greatly enhance the understanding of the skeletal adaptations following facial skeletal surgery and identify specific morphology and/or specific regions that contribute to the variability in the skeletal response (Specific Aim 1) and nerve recovery (Specific Aim 2). Specific Aim 3 represents, to the best of our knowledge, the first prospective longitudinal comparison of the effectiveness and recovery pattern of temporary skeletal anchorage during orthodontic treatment versus orthognathic surgery. The successful completion of this project will provide additional knowledge to facilitate improvement of procedural techniques and treatment outcomes. This project represents the next step in achieving our overall goal of improving the outcomes and treatment options of patients seeking treatment for dentofacial disharmony by developing evidence-based treatments, incorporating diagnostic, procedural, and skeletal response information.